Tutorial as jupyter notebook (not for merging!)

[iosonofabio]

Hi all,

My initial attempts at building a Jupyter notebook version of our tutorial.rst using sphinx-gallery. See the discussion in #667 for further info.

NOTE: This PR is not meant for merging but rather just to collect feedback. It seems like a straightforward solution might not be obvious, so let's discuss a little and see what we can find out.